Lighting on a model railroad covers several different topics: lighting the trains themselves, building and other scenic lights, and lineside signals. Today almost all of these are done using Light Emitting Diodes, or LEDs, although some models still use low-voltage bulbs. In normal operation, bulbs have lifespans in hundreds of hours, and won’t likely burn out during a model’s useful life. However LEDs have the benefit of using less power and producing less heat (bulbs can produce enough heat to melt plastic models). LEDs also last for tens of thousands of hours, and will easily outlive most modelers.
Another aspect of lighting is the actual room lighting. This has a “color” (often described as “warm” or “cool” depending on the light source), and the color of the room light affects how the color of model lights (and the models themselves) are perceived. This, however, is more of a layout design topic than an electrical one, and is covered in the Layout Lighting subsection of the Layout Construction section.